Applications of Refraction Microtremor Done Right, and Pitfalls of Microtremor Arrays Done Wrong

Abstract eng:
The geotechnical industry has widely adopted the refraction microtremor shear-wave velocity measurement technique since Louie’s original paper on the method in 2001, and is accepted by building authorities around the world. After successful initial commercialization, the developers have further adapted the method to new applications. Clark County and the City of Henderson, Nevada populated their Earthquake Parcel Map with over 10,000 site measurements for building code enforcement, made over a three-year period. A new 2D refraction microtremor analysis now allows engineers to image lateral shear-wave velocity variations and do passive subsurface imaging. The developers have extended the range of 2D refraction microtremor analysis to several kilometers depth, completing several deep-basin shear-wave velocity measurement programs for the USGS. We present an uncertainty analysis that incorporates variance in picking of the dispersion curves together with trade-offs in the modeled shear-wave velocities. The uncertainty analysis extends to 2D refraction microtremor sections. The goal is to provide users with confidence limits on the results when using them for site classification, geological interpretation, or community velocity models for scenario shaking computations. Unfortunately, any useful and popular measurement technique can be abused. Practitioners must carefully follow correct data collection, analysis, interpretation, and modeling procedures, or the outcomes cannot be labeled “refraction microtremor” or “ReMi™” results. Inexperienced or ill-informed practitioners have at times failed to produce correct shearwave velocities, due to either improper data acquisition or faulty analysis techniques. We present some of the common mistakes, and provide solutions with the objective of establishing a “best practices” template for getting consistent, reliable models from refraction microtremor measurements.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket